Biochemical mechanism(s) of action of gonadotropin-releasing factor (GnRH) is being pursued. Currently the control of LH synthesis is being studied. For the incorporation experiments, two model systems are employed: Intact pituitaries from 25 day old female rats and monolayer culture prepared from diestrus rats. Using both systems we have demonstrated the incorporation of (H3) glucosamine and (H3) proline into LH. LH is characterized by immunoprecipitation technique. GnRH increased in vitro incorporation of (H3) glucosamine into immunoprecipitable LH. The kinetics of LH synthesis and glycosylation are under investigation. Other aspects of investigation include isolation of Poly A containing messenger RNA fraction from the pituitary and its translation into LH using in vitro protein synthesizing systems. The possible correlation between estradiol receptor levels in the pituitary and the sensitivity of the pituitary to GnRH is also being investigated.